Electrocatalytic oxidation of ascorbate at electrodes, covered with polyaniline and sulfonated polyaniline, has been studied by in situ Raman spectroelectrochemistry with the green laser excitation (532 nm). Characteristic Raman features have been identified and their changes during electrooxidation of ascorbate have been analysed. It has been shown that an increase of ascorbate concentration causes an increase of the relative content of the reduced polyaniline form within the film. From this, it has been concluded that electrocatalytic oxidation of ascorbate proceeds within a polyaniline film rather than at an outer polyaniline/solution boundary, i.e. electrooxidation follows a redox-catalysis mechanism. (c) 2006 Elsevier Ltd. All rights reserved.